Irrigation Pump with Ablation and Non-Ablation Operational Modes

ABSTRACT

A pump includes a cylinder, a piston and a controller. The cylinder has first and second ends and includes first and second inlet-outlet ports, each of the first and second inlet-outlet ports is configured to alternately intake a fluid to the cylinder and output the fluid from the cylinder. The piston is configured to be moved within the cylinder between the first and second ends by alternately reversing a direction of movement of the piston, so as to pump the fluid through the first and second inlet-outlet ports. The controller is configured to control the movement of the piston within the cylinder, including: (a) choosing between first and second operational modes, (b) in the first operational mode, controlling the piston to oscillate over a predefined interval that does not exceed a predefined distance from the first end or from the second end, and (c) in the second operational mode, controlling the piston to move at a selected speed between the first end and the second end.

PRIORITY CLAIM

This application claims the benefit of U.S. Provisional PatentApplication 62/786,404, filed Dec. 29, 2018. This application is relatedto a U.S. Patent Application entitled “Dual-Action Irrigation Pump withVariable Speed to Provide Constant Fluid Flow,” Attorney docket numberID-1557/BIO6047USNP1/2002-2047, each of the prior applications is herebyincorporated by reference as if set forth in full herein thisapplication.

FIELD OF THE INVENTION

The present invention relates generally to pumps, and particularly tomedical irrigation pumps.

BACKGROUND OF THE INVENTION

Irrigation pumps are used in some medical procedures. Various techniqueshave been developed for improving performance of medical irrigationpumps.

For example, U.S. Pat. No. 6,913,933 describes a method for improvingthe fluid dispense rate in a metering system utilizing speed includesthe steps of modifying the fluid flow rate profile during a portionthereof so as substantially increase or decrease the speed of the motorduring certain portions of a metering cycle in order to improve theefficiency of the metering system.

U.S. Pat. No. 5,066,282 describes a disposable, positive-displacementpiston pump, having a polycarbonate body, a piston, an inlet valve, andan outlet valve. The outlet valve is connected to an exit chamber, whichis separated from the exit valve by an elastomeric membrane. Theelastomeric membrane encloses an accumulation chamber which is filledwith a fluid such as air under atmospheric pressure. Pulsations inoutlet pressure caused by stroking of the piston are dampened by theflexing action of the elastomeric membrane, compressing the fluid withinthe accumulator chamber.

U.S. Pat. No. 9,622,814 describes an ablation catheter which controlsthe temperature and reduces the coagulation of biological fluids on anelectrode of a catheter, prevents the impedance rise of tissue incontact with the electrode, and maximizes the potential energy transferto the tissue, thereby allowing an increase in the lesion size producedby the ablation. The electrode includes passages positioned to allowsaline flow out of an inner cavity of the electrode. This fluid flow ispulsatile to increase turbulence, reducing areas of stagnant flow, andproduces a desired cooling effect.

SUMMARY OF THE INVENTION

An embodiment of the present invention that is described herein providesa pump including a cylinder, a piston and a controller. The cylinderincludes first and second inlet-outlet ports, each of the first andsecond inlet-outlet ports is configured to alternately intake a fluid tothe cylinder and output the fluid from the cylinder. The piston isconfigured to be moved within the cylinder in a periodic cycle thatalternately reverses a direction of movement of the piston, so as topump the fluid through the first and second inlet-outlet ports. Thecontroller is configured to control the movement of the piston withinthe cylinder, including setting to the piston: (a) a first speed, duringa first predefined interval that precedes reversing the direction ofmovement, (b) a second speed, larger than the first speed, during asecond predefined interval that follows reversing the direction, and (c)a baseline speed, smaller than the first speed, outside the first andsecond intervals.

In some embodiments, the pump includes a piston position sensingassembly (PPSA), which is configured to produce a control signalindicative of a position of the piston within the cylinder, thecontroller is configured to receive the control signal, and to controlthe movement of the piston based on the control signal. In otherembodiments, the controller is configured to control the movement of thepiston between first and second ends of the cylinder, the PPSA includes(a) a first electrical switch configured to produce a first positionsignal when the piston is situated within a predefined distance from thefirst end, and (b) a second electrical switch configured to produce asecond position signal when the piston is situated within a predefineddistance from the second end, and the PPSA is configured to produce thecontrol signal based on at least one of the first and second positionsignals.

In an embodiment, the controller is configured to control a given volumeof the fluid to be pumped through the first and second inlet-outletports during a first time period including at least the first and secondpredefined intervals, and to control the same given volume of the fluidto be pumped through the first and second inlet-outlet ports during asecond time period that is approximately equal to the first time period,when the piston is outside the first and second intervals. In anotherembodiment, at least one of the first and second inlet-outlet ports iscoupled to a fluid reservoir via a first pipe, and to a catheter via asecond pipe, so as to irrigate tissue with the fluid during a medicalprocedure.

There is additionally provided, in accordance with an embodiment of thepresent invention, a method for pumping a fluid in a medical procedure,the method includes, in a pump including a cylinder having first andsecond inlet-outlet ports for alternately in-taking a fluid to thecylinder and outputting the fluid from the cylinder by each of the firstand second inlet-outlet ports, moving a piston within the cylinder in aperiodic cycle that alternately reverses a direction of movement of thepiston so as to pump the fluid through the first and second inlet-outletports. The movement of the piston within the cylinder is controlled,including setting to the piston: (a) a first speed, during a firstpredefined interval that precedes reversing the direction of movement,(b) a second speed, larger than the first speed, during a secondpredefined interval that follows reversing the direction, and (c) abaseline speed, smaller than the first speed, outside the first andsecond intervals.

There is further provided, in accordance with an embodiment of thepresent invention, a pump that includes a cylinder, a piston and acontroller. The cylinder has first and second ends and includes firstand second inlet-outlet ports, each of the first and second inlet-outletports is configured to alternately intake a fluid to the cylinder andoutput the fluid from the cylinder. The piston is configured to be movedwithin the cylinder between the first and second ends by alternatelyreversing a direction of movement of the piston, so as to pump the fluidthrough the first and second inlet-outlet ports. The controller isconfigured to control the movement of the piston within the cylinder,including: (a) choosing between first and second operational modes, (b)in the first operational mode, controlling the piston to oscillate overa predefined interval that does not exceed a predefined distance fromthe first end or from the second end, and (c) in the second operationalmode, controlling the piston to move at a selected speed between thefirst end and the second end.

In some embodiments, the controller is configured to receive a signalindicative of a position of the piston within the cylinder, and tocontrol the movement of the piston based on the signal. In otherembodiments, at least one of the first and second inlet-outlet ports iscoupled to a fluid reservoir via a first pipe, and to a catheter via asecond pipe, so as to irrigate tissue with the fluid during a medicalprocedure. In yet other embodiments, the medical procedure includestissue ablation by the catheter, and the controller is configured tochoose the second operational mode in response to receiving a controlsignal indicative of the tissue ablation.

In an embodiment, the tissue ablation includes positioning the catheterat first and second ablation sites, and, in the second operational mode,the controller is configured to control the piston to: (a) move at afirst selected speed when the catheter is positioned at the firstablation site, and (b) move at a second, different, selected speed whenthe catheter is positioned at the second ablation site. In anotherembodiment, in the second operational mode, the controller is configuredto control the piston to move at a constant speed. In yet anotherembodiment, in the second operational mode, the controller is configuredto control the piston to move at a variable speed.

There is additionally provided, in accordance with an embodiment of thepresent invention, a method for pumping a fluid in a medical procedure,the method includes in a pump including a cylinder having first andsecond ends and including first and second inlet-outlet ports foralternately in-taking a fluid to the cylinder and outputting the fluidfrom the cylinder by each of the first and second inlet-outlet ports,moving a piston within the cylinder between the first and second ends byalternately reversing a direction of movement of the piston, so as topump the fluid through the first and second inlet-outlet ports. Themovement of the piston within the cylinder, including: (a) choosingbetween first and second operational modes, (b) in the first operationalmode, controlling the piston to oscillate over a predefined intervalthat does not exceed a predefined distance from the first end or fromthe second end, and (c) in the second operational mode, controlling thepiston to move at a selected speed between the first end and the secondend.

There is further provided, in accordance with an embodiment of thepresent invention, a pump that includes a cylinder, a piston and acontroller. The cylinder has first and second ends and including firstand second inlet-outlet ports, each of the first and second inlet-outletports is configured to alternately intake a fluid to the cylinder andoutput the fluid from the cylinder. The piston is configured to be movedwithin the cylinder between the first and second ends by alternatelyreversing a direction of movement of the piston, so as to pump the fluidthrough the first and second inlet-outlet ports. The controller isconfigured to control the movement of the piston within the cylinder,including: (a) choosing between first and second operational modes, (b)in the first operational mode, controlling the piston to remainstationary at a predefined distance larger than zero from the first endor from the second end, and (c) in the second operational mode,controlling the piston to move at a selected speed between the first endand the second end.

The present invention will be more fully understood from the followingdetailed description of the embodiments thereof, taken together with thedrawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, pictorial illustration of a catheter-basedablation system, in accordance with an embodiment of the presentinvention;

FIG. 2 is a schematic, side view of an irrigation pump of an ablationsystem, in accordance with an embodiment of the present invention;

FIG. 3A is a schematic, pictorial illustration of a movement of a pistonwithin a cylinder of a medical irrigation pump, in accordance with anembodiment of the present invention;

FIG. 3B is a graph that schematically illustrates a movement profile ofa piston in a cylinder of a medical irrigation pump, in accordance withan embodiment of the present invention;

FIG. 4 is a flow chart that schematically illustrates a method forflowing a constant output of irrigation fluid over time, in accordancewith an embodiment of the present invention;

FIG. 5 is a schematic, pictorial illustration of a movement profile of apiston in an irrigation pump used in a cardiac ablation procedure, inaccordance with another embodiment of the present invention; and

FIG. 6 is a flow chart that schematically illustrates a method forpumping irrigation fluid in a cardiac ablation procedure, in accordancewith another embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS Overview

Some cardiac procedures comprise tissue ablation, such asradio-frequency (RF) ablation, carried out at predefined sites of apatient heart for treating arrhythmia. An RF ablation system typicallycomprises ablation electrodes that are coupled to a distal end of acatheter, and a navigation subsystem, such as a magnetic positiontracking subsystem, for navigating the catheter distal-end to theablation sites. The RF ablation system further comprises an irrigationassembly for irrigating the ablated tissue with irrigation fluids. It isimportant to irrigate the tissue before and during ablation, usingcontrolled irrigation parameters such as flow rates, without introducingelectrical noise that may interfere with magnetic fields of the magneticposition tracking subsystem.

Embodiments of the present invention that are described hereinbelowprovide methods and apparatus for improving control of irrigationparameters during ablation procedures. In some embodiments, anirrigation assembly comprises (a) a fluid reservoir containing theirrigation fluid, (b) one or more irrigation openings at a catheterdistal-end, for irrigating tissue of a patient heart, and (c) a pump,which is configured to pump the irrigation fluid between the reservoirand irrigation openings.

In some embodiments, the pump comprises a cylinder having first andsecond ends, also referred to herein as walls, and comprising first andsecond inlet-outlet ports, each of which is coupled to the reservoir andthe catheter. Each of the inlet-outlet ports is configured toalternately, intake the fluid from the reservoir to the cylinder andoutput the fluid from the cylinder to the catheter distal end. The pumpcomprises a piston, which is configured to be moved within the cylinderbetween the first and second walls by alternately reversing thedirection of movement of the piston, so as to pump the fluid through thefirst and second inlet-outlet ports.

In some embodiments, the pump further comprises a controller, which isconfigured to control the movement of the piston within the cylinder.The controller is configured to choose between ablation and non-ablationoperational modes of the pump. In the ablation operational mode, thecontroller is configured to control the piston to move at a selectedspeed between the first wall and the second wall, so as to irrigate theablated site. In the non-ablation operational mode, the controller isconfigured to control the piston to oscillate over a predefined intervalthat does not exceed a predefined distance from the first wall or fromthe second wall of the cylinder, so as to maintain low irrigation flowsbetween the tissue ablations. In some embodiments, the controller isconfigured to receive a signal indicative of the position of the pistonwithin the cylinder, and to control the movement of the piston based onthe signal. The controller is further configured to receive a controlsignal, and to choose between the non-ablation and ablation operationalmodes based on the control signal.

In other embodiments, the piston is configured to be moved between thewalls, in a periodic cycle that alternately reverses a direction ofmovement of the piston at the walls, so as to pump the fluid through thefirst and second inlet-outlet ports. In such embodiments, the controlleris configured to control the movement of the piston between the walls,including setting to the piston: (a) a first speed, during a firstpreset interval from the wall that precedes reversing the direction ofmovement, (b) a second speed, larger than the first speed, during asecond preset interval from the wall that follows reversing thedirection, and (c) a baseline speed, smaller than the first speed,outside the first and second preset intervals. The controller isconfigured to set the size of the first and second preset intervals andthe corresponding first and second speeds, in order to control the flowrate of the irrigation fluid relative to the specified flow rate, andwhen applicable, to maintain a constant flow rate through theinlet-outlet ports when the piston reverses directions.

The disclosed techniques improve the patient safety and the quality ofablation procedures by improving control of the irrigation parametersduring ablation and between ablations of the heart tissue.

In the context of the present invention and in the claims, the terms“pump” and “irrigation pump” may refer to a dual-action pump or anyother suitable type of pump.

System Description

FIG. 1 is a schematic, pictorial illustration of a catheter-basedablation system 20, in accordance with an embodiment of the presentinvention. System 20 comprises a catheter 21, having a shaft distal end22 that is navigated by a physician 30 into a heart 26 of a patient 28via the vascular system. In some embodiments, physician 30 inserts shaftdistal end 22 through a sheath 23, while manipulating distal end 22using a manipulator 32 located at the proximal end of catheter 21.

Reference is now made to an inset 25. In some embodiments, system 20comprises a magnetic sensor 51, also referred to herein as a magneticposition tracking sensor, or sensor 51 for brevity, and an ablationcatheter 50, which are coupled to distal end 22.

In the embodiments, catheter 21 may be used for various procedures, suchas electrophysiological (EP) mapping of heart 26 and for ablatingselected tissue of heart 26. Catheter 21 comprises irrigation openingsfor irrigating tissue of heart 26 during the EP procedure and inparticular during ablation as will be described in detail below.

In some embodiments, the proximal end of catheter 21 is electricallyconnected to a control console 48 and, in parallel, to an irrigationassembly 11 that supplies irrigation fluid 88, also referred to hereinas fluid 88 for brevity, for the ablation and other procedures carriedout by system 20. In an embodiment, console 48 comprises a processor 39,a controller 33 and interface circuit 38, which is configured toexchange signals between processor 39 and/or controller 33, and variouscomponents, modules and assemblies of system 20, as will be described indetail below.

In some embodiments, interface circuits 38 are configured to receiveelectrical signals from catheter 21 and other sensors of system 20.Circuits 38 are further configured to send electrical signals, receivedfrom processor 39 and controller 33, to various components andassemblies of system 20, such as applying power via catheter 21 forablating tissue of heart 26, and for controlling the other componentsand assemblies of system 20. For example, during ablation, catheter 21is configured to irrigate the ablated tissue with irrigation fluid aswill be described in detail below. In an embodiment, processor 39 isconfigured to control ablation electrodes (not shown), disposed atdistal end 22, to apply radiofrequency (RF) energy to tissue of heart26. As will be described in detail below, controller 33 is configured toapply irrigation fluid 88 to the tissue, e.g., during the ablationprocedure.

In some embodiments, system 20 comprises multiple (e.g., three) magneticfield generators 36, configured to produce alternating magnetic fields.Field generators 36 are placed at known positions external to patient28, for example, below a patient table 29.

In some embodiments, console 48 further comprises a display 27, and adriver circuit (not shown), which is configured to drive magnetic fieldgenerators 36.

During an EP procedure physician 30 navigates distal end 22 of catheter21 in heart 26. In some embodiments, in response to the magnetic fieldsirradiated from field generators 36, magnetic sensor 51 is configured toproduce a position signal, indicative of the position of distal end 22in heart 26.

In some embodiments, based on the position signal received from sensor51, processor 39 is configured to display, e.g., on display 27, theposition of distal end 22 in the coordinate system of system 20.

This method of position sensing is implemented, for example, in theCARTO™ system, produced by Biosense Webster Inc. (Irvine, Calif.) and isdescribed in detail in U.S. Pat. Nos. 5,391,199, 6,690,963, 6,484,118,6,239,724, 6,618,612 and 6,332,089, in PCT Patent Publication WO96/05768, and in U.S. Patent Application Publications 2002/0065455 A1,2003/0120150 A1 and 2004/0068178 A1.

In some embodiments, irrigation assembly 11 comprises a pump 44, in thepresent example an irrigation pump whose structure and functionality aredescribed, for example, in

FIGS. 2, 3A and 5 below. Irrigation assembly 11 further comprises afluid reservoir 55, which is configured to contain irrigation fluid 88,such as a saline solution or any other type of fluid suitable forirrigating tissue of heart 26.

In some embodiments, irrigation assembly 11 comprises tubes 52A and 52B,configured to flow fluid 88 between reservoir 55 and pump 44. Irrigationassembly 11 further comprises tubes 49A and 49B, configured to flowfluid 88 between pump 44 and catheter 21.

In some embodiments, controller 33 is configured to receive, via a cable53, electrical signals indicative of control parameters of irrigationassembly 11. Based on the control parameters, controller 33 isconfigured to control the flow of fluid 88 to distal end 22 and withinirrigation assembly 11. Embodiments of method and apparatus forcontrolling the flow of fluid 88 are described in detail in FIGS. 2-6below.

Processor 39 and/or controller 33 typically comprise a general-purposeprocessor or controller, which is programmed in software to carry outthe functions described herein. The software may be downloaded toProcessor 39 and controller 33 in electronic form, over a network, forexample, or it may, alternatively or additionally, be provided and/orstored on non-transitory tangible media, such as magnetic, optical, orelectronic memory.

Controlling Fluid Pumping in a Pump

FIG. 2 is a schematic, side view of pump 44, in accordance with anembodiment of the present invention. In some embodiments, pump 44comprises a cylinder 111, which is configured to contain irrigationfluid 88 for irrigating tissue of heart 26. Pump 44 further comprises apiston 99, which is configured to be moved within cylinder 111, e.g.,along a shaft 105, using a stepper motor (not shown), or any suitabletype of motion apparatus, such as but not limited to any other type ofsuitable motor or actuator. In the example of pump 44, cylinder 111 andpiston 99 have, both, a circular cross-section. Pump 44 can be amodified version of pump 10 shown and described in U.S. ProvisionalPatent Application 62/786,404, filed Dec. 29, 2018.

In the context of the present patent application and in the claims, theterm “cylinder” refers, as a term of art, to any suitable container inwhich piston 99, or any other suitable type of piston, moves. In thiscontext, the cylinder and the piston may have any suitablecross-section, not necessarily circular.

In some embodiments, cylinder 111 has a left wall 66 and a right wall77, also referred to herein, respectively, as “first and second ends” ofcylinder 111, or as “walls 66 and 77,” for brevity. In some embodiments,cylinder 111 comprises inlet-outlet ports 112 and 114, formed in walls66 and 77, respectively.

In the context of the present patent application and in the claims, therespective terms “inlet-outlet ports 112 and 114,” “port 112 and 114,”and “first and second inlet-outlet ports,” are used interchangeably andrefer to openings in cylinder 111. In an embodiment, each of the firstand second inlet-outlet ports is configured to alternately, intake fluid88 to cylinder 111 and output fluid 88 from cylinder 111.

In some embodiments, each of inlet-outlet ports 112 and 114 may have twoopenings. Note that in the side view of FIG. 2, both openings are in thesame plane (which is orthogonal to the plane of FIG. 2), therefore thesecond opening is hidden behind the first opening and both openings areshown as a single opening. In some embodiments, the first opening ofinlet-outlet port 112 is coupled, via a valve 122A, to tube 52A, and thesecond opening of inlet-outlet port 112 is coupled, via a valve 122B, totube 49A. Similarly, the first opening of inlet-outlet port 114 iscoupled, via a valve 124A, to tube 52B, and the second opening ofinlet-outlet port 114 is coupled, via a valve 124B, to tube 49B.

In some embodiments, tubes 49A and 49B are coupled to a common tube 49C,which is also coupled to catheter 21. Similarly, tubes 52A and 52B arecoupled to a common tube 52C, which is also coupled to reservoir 55.

In some embodiments, in a pump, such as pump 44, each of inlet-outletports 112 and 114 exchanges fluid 88 with two entities, in the presentexample, reservoir 55 and catheter 21. Each of valves 122A, 122B, 124Aand 124B, is configured to enable the flow of fluid 88 in one directionand to block the flow of fluid 88 in the opposite direction (e.g., aone-way valve), and also to reverse the flow direction. Controller 33 isconfigured to control the flow direction of fluid 88 by switching themovement direction of piston 99. In such embodiments, the movement ofpiston 99 determines the flow direction in the aforementioned valves.For example, when piston 99 is moved toward wall 77, valve 122A intakesfluid 88 from reservoir 55, via tubes 52C and 52A, into cylinder 111,and at the same time, valve 124B outputs fluid 88 from cylinder 111, viatubes 49B and 49C, into catheter 21. In alternative embodiments,controller 33 is configured to control, via electrical cables 53, theflow direction of valves 122A, 122B, 124A and 124B. In this embodiment,valves 122A, 122B, 124A and 124B can be in the form electricallyoperated solenoid valves.

In some embodiments, piston 99 is moved within cylinder 111 in aperiodic cycle that alternately reverses the direction of movement ofpiston 99, so as to pump fluid 88 through inlet-outlet ports 112 and114. For example, when piston 99 is moved in a reversed direction towardleft wall 66, valve 122B enables outflow of fluid 88 that is disposedbetween piston 99 and wall 66 to flows from pump 44, via port 112 andtubes 49A and 49C, into catheter 21 for irrigating tissue of heart 26.At the same time, valve 124A enables flow of fluid 88 from reservoir 55,via tubes 52C and 52B and through port 114, into cylinder 111.

In some embodiments, pump 44 comprises a piston position sensingassembly (PPSA) 54, which is configured to sense the position of piston99 along shaft 105, and to produce a signal indicative of the positionof piston 99 within cylinder 111. In some embodiments, PPSA 54 comprisesany suitable type of position sensor. In the example of FIG. 2, PPSA 54comprises electrical switches 56A and 56B, disposed in close proximityto walls 66 and 77, respectively. In some embodiments, electricalswitches 56A and 56B are electrically coupled to a controller 57 that iselectrically connected to controller 33. In other embodiments,electrical switches 56A and 56B may be electrically coupled directly tocontroller 33.

In some embodiments, PPSA 54 may be calibrated during the assembly ofsystem 20 and/or at least prior to the first medical procedure thatrequires irrigation. During the calibration, controller 33 controls themovement of piston along shaft 105, between walls 66 and 77. When pistonreaches wall 66, electrical switch 56A sends to controller 57, a signalindicative of the position of piston 99. Subsequently, controller 33controls the movement of piston 99, within cylinder 111, to wall 77, andcount steps of the stepper motor. When piston 99 reaches wall 77,electrical switch 56B sends to controller 57, a signal indicative of theposition of piston 99, and controller 57 concludes the calibration. Insome embodiments, based on the calibration, the counted number of stepsand the direction thereof, controller 57 may send to controller 33 theaforementioned signal indicative of the position of piston 99 withincylinder 111.

In alternative embodiments, piston 99 may not make physical contact withwalls 66 and 77, but approaches the walls, e.g., within a predefineddistance of a few millimeters or any other suitable distance.

In other embodiments, PPSA 54 may have any other suitable configuration,using any suitable technique for producing the signals indicative of thecurrent position of piston 99 within cylinder 111.

This particular configuration of irrigation assembly 11 and system 20 isshown by way of example, in order to illustrate certain problems thatare addressed by embodiments of the present invention and to demonstratethe application of these embodiments in enhancing the performance ofsuch a system. Embodiments of the present invention, however, are by nomeans limited to this specific sort of example system, and theprinciples described herein may similarly be applied to other sorts ofmedical ablation and/or irrigation systems.

FIG. 3A is a schematic, pictorial illustration of a movement of piston99 within cylinder 111 during irrigation, in accordance with anembodiment of the present invention. In some embodiments, controller 33is configured to control the movement of piston 99 in a periodic cyclethat alternately reverses the direction of movement of piston 99 using amovement profile 80, so as to pump fluid 88 at a constant rate.

Note that controller 33 has to change the movement direction when piston99 reaches any of walls 66 and 77, therefore, piston 99 stands still(i.e., remains stationary) at walls 66 and 77 before changing direction.In other words, the movement speed of piston 99 when positioned at walls66 and 77 is zero, and therefore, fluid 88 is not pumped at thesepositions. In an embodiment, controller 33 is configured to maintain theconstant flow rate of fluid 88 using a technique described in FIG. 3Bbelow.

In other embodiments, piston 99 does not make physical contact with atleast one of walls 66 and 77. In such embodiments, controller 33 maychange the movement direction before piston 99 reaches any of walls 66and 77. For example, controller 33 may change the movement direction ofpiston 99 when piston 99 approaches wall 66 within a predeterminedinterval of a few millimeters, or within any other suitable predefinedinterval.

Controlling Constant Rate of Fluid Pumping Using a Pump

FIG. 3B is a graph 100 that schematically illustrates a movement profileof piston 99 within cylinder 111 during irrigation, in accordance withan embodiment of the present invention. In some embodiments, graph 100shows the movement speed of piston 99 as a function of the position ofpiston 99 in accordance with movement profile 80 shown in FIG. 3A above.For the sake of conceptual clarity, graph 100 is divided into multiplesection corresponding to the position of piston 99 within cylinder 111.

In some embodiments, when piston 99 is positioned at section 164, whichis situated between walls 66 and 77 as shown in FIG. 3A, controller 33is configured to move piston 99 toward wall 77 at a baseline speed,referred to as “BLS” on the movement speed axis of graph 100. Note thatthe BLS, depends the dimensions of cylinder 111 defining the volume offluid 88, and also based on the predefined parameters of the ablationprocedure, such as but not limited to the ablation power and the targettemperature of the ablated tissue.

As described above, piston 99 is moved toward wall 77 and PPSA 54 sendssignals indicative of the respective positions of piston 99 withincylinder 111. Note that controller 33 reverses the movement direction ofpiston 99 upon reaching walls 66 and 77, or in close proximity to thewall.

In some embodiments, when piston 99 is at a predefined interval 176(e.g., about 1 mm or any other suitable interval) from wall 77,controller 33 receives from PPSA a signal indicative of thecorresponding position thereof, and in response, controller 33 sets topiston a first speed, S1, which is larger than BLS.

In the context of the present disclosure and in the claims, the terms“about” or “approximately” for any numerical values or ranges indicate asuitable dimensional tolerance that allows the part or collection ofcomponents to function for its intended purpose as described herein.More specifically, “about” or “approximately” may refer to the range ofvalues ±20% of the recited value, e.g. “about 90%” may refer to therange of values from 71% to 99%.

In some embodiments, when piston 99 is in close proximity (e.g. about 2mm) to wall 77, controller may reduce the speed of piston 99 to acomplete stop, shown as a speed “S0” at point 177, which corresponds topiston 99 having physical contact with wall 77, or is within apredetermined interval from wall 77.

In some embodiments, in response to receiving from PPSA 54 a signalindicating that piston 99 makes physical contact with wall 77 (or iswithin a predetermined interval therefrom), controller 33 is configuredto reverse the movement direction of piston 99 toward wall 66, and toset to piston 99 a movement speed S2 shown at a predefined interval 178of graph 100. Note that intervals 176 and 178 may overlap in position(e.g., both are in proximity to wall 77), but having piston moved indifferent directions, and therefore, are shown as different intervals ingraph 100.

In some embodiments, controller 33 is configured to compensate for thereduced flow rate of pump 44 caused by the complete stop at wall 77(corresponding to point 177), by setting to piston 99 speed S1 atinterval 176 that precedes reversing the direction of movement, andspeed S2 at interval 178 that follows reversing the direction ofmovement. As described above, speed S2 is larger than S1 and both speedsS1 and S2 are larger than BLS, this sequence results in a flow rateincrease of pump 44 so as to compensate for the reduced flow rate whenpiston is situated in close proximity to, and is making contact withwall 77.

In such embodiments, at a first time interval referred to herein as asection 174 of graph 100, pump 44 flows (e.g., to catheter 21) at agiven time, volume of fluid 88 similar to the volume flown by pump 44 ifpiston 99 were moved at the BLS speed. In other words, controller 33sets pump 44 to retain constant flow of fluid 88 also when reversing thedirection of movement at walls 66 and 77.

In some embodiments, controller 33 is configured to set speeds S1 and S2and the physical dimensions of intervals 176 and 178 using any suitablearrangement that obtains the aforementioned constant flow of fluid 88 bypump 44. In such embodiments, controller 33 may set intervals 176 and178 to have similar or different physical travel and/or durationrelative to one another. For example, controller 33 may set speed S2substantially larger than speed S1, and interval 178 shorter thaninterval 176, or may use any other suitable combination of speeds andinterval durations for optimizing the flow rate of pump 44.

In some embodiments, in response to receiving from PPSA 54 a signalindicating that piston concluded the travel in interval 178, controller33 controls the movement of piston 99 toward wall 66 at a predefinedinterval 179 situated outside intervals 176 and 178, and sets the speedof piston 99 to BLS.

In some embodiments, in response to receiving from PPSA 54 a signalindicating that piston concluded the travel in interval 179, controller33 sets the speed of piston 99 to S1 at a predefined interval 165 thatprecedes reversing the direction of movement at wall 66.

Using the same sequence described above for point 177, in response toreceiving from PPSA 54 a signal indicating that piston concluded thetravel in interval 165, controller 33 reduces the moving speed of piston99 to a complete stop at point 166, which corresponds to piston 99having physical contact with wall 66 or is within a predeterminedinterval therefrom.

In some embodiments, in response to receiving from PPSA 54 a signalindicating that piston 99 makes physical contact with (or is within apredetermined interval from) wall 66, controller 33 is configured toreverse the movement direction of piston 99 toward wall 77, and to setto piston 99 movement speed S2 at a predefined interval 167 that followsreversing the direction of movement.

In some embodiments, in response to receiving from PPSA 54 a signalindicating that piston 99 has concluded travelling along interval 167,controller 33 controls the movement of piston 99 toward wall 77 atinterval 164 situated outside intervals 165 and 167, and sets the speedof piston 99 to BLS.

In some embodiments, at a second time interval referred to herein as asection 169 of graph 100, pump 44 flows (e.g., to catheter 21) at agiven time, volume of fluid 88 similar to the volume flown by pump 44 ifpiston 99 were moved at the BLS speed, as described for section 174above.

In some embodiments, controller 33 is configured, in response to asignal received from processor 39, to move piston 99 within cylinder 111in a periodic cycle that alternately reverses the direction of movementof piston 99, so as to pump fluid 88 through inlet-outlet ports 112 and114. When physician 30 decides to stop irrigating tissue of heart 26, orwhen system 20 stops the irrigation automatically, processor 39 sends asignal to controller 33 to stop moving piston 99 within cylinder 111,and the irrigation stops.

FIG. 4 is a flow chart 200 that schematically illustrates a method forflowing a constant output of irrigation fluid 88 by pump 44, inaccordance with an embodiment of the present invention. The methodbegins at a piston movement step 202 with controller 33 receives acontrol signal from processor 39 to irrigate tissue of heart 26 withirrigation fluid 88, and controlling the movement of piston 99 inselected direction at baseline speed (BLS), as described in interval 164of FIG. 3B above.

At a position signal receiving step 204, controller receives from PPSA54 signals indicative of the respective positions of piston 99 movedtoward wall 77, as described in FIG. 3B above. At a first speed settingstep 206, in response to receiving from PPSA 54 a signal indicating thatpiston concluded the travel in interval 164, controller 33 controls themovement of piston 99 toward wall 77 at speed S1 along interval 165.Subsequently, when approaching wall 77, controller 33 reduces the speedof piston 99 to a complete stop when reaching wall 77, as described inFIG. 3B above.

At a second speed setting step 208, in response to receiving from PPSA54 a signal indicating that piston makes contact with or approaching(e.g., within the aforementioned predetermined interval from) wall 77,controller 33 reverses the moving direction and controls the movement ofpiston 99 toward wall 66 at speed S2 along interval 167, as described inFIG. 3B above. At a third speed setting step 210, in response toreceiving from PPSA 54 a signal indicating that piston concluded thetravel in interval 167, controller 33 sets the movements of piston 99toward wall 66 at BLS along interval 179, as described in FIG. 3B above.In some embodiments, step 210 is typically concluded when controller 33receives from PPSA 54 a signal indicating that piston concluded thetravel in interval 179, and the method loops back to step 206 andcontinues until controller 33 receives from processor 39 a controlsignal to stop irrigating tissue of heart 26.

Controlling Irrigation Pump Between and During Ablation

FIG. 5 is a schematic, pictorial illustration of a movement profile ofpiston 99 in pump 44 used in a cardiac ablation procedure, in accordancewith another embodiment of the present invention. In some embodiments,controller 33 is configured to operate pump 44 in two operational modes,referred to herein as first and second operational modes.

In some embodiments, the first operational mode is carried out at apredefined interval 311 that does not exceed a predefined distance, suchas but not limited to about 0.5 cm from wall 66 or 77. At the firstoperational mode, controller 33 is configured to operate pump 44 at anon-ablation state 333, such that distal end 22 is operated by physician30 in heart 26, but is not ablating tissue of heart 26. Note that in anablation state that will be described in detail below, it is importantto pump fluid 88 without changing the movement direction of piston 99,therefore, non-ablation state 333 is used by controller 33 forpositioning piston 99 in close proximity to one of walls 66 and 77, andif needed to carry out a specified irrigation within heart 26 asdescribed in detail below.

In some embodiments, in non-ablation state 333, controller 33 isconfigured to control piston 99 to oscillate over predefined interval311. In such embodiments, piston 99 is moved within interval 311 in aperiodic cycle that alternately reverses the direction of movement ofpiston 99, so as to pump fluid 88 through inlet-outlet ports 112 and114. Note that by oscillating piston 99 within interval 311, irrigationassembly 11 irrigates tissue of heart 26 with pulses of fluid 88,defined by the width of interval 311 and by the movement speed of piston99, or in other words, by the cycle time of one oscillation, e.g.,starting and finishing at wall 66.

In other embodiments, controller 33 may control the movement of piston99 within interval 311 to pump a constant flow of fluid 88, for example,by applying the technique described in FIGS. 3B and 4 above.

In alternative embodiments, controller 33 may control the movement ofpiston 99 using any other suitable movement profile. For example, inresponse to instruction signals from processor 39, controller 33 maycontrol the speed of piston 99 to change with time, so as to increase ordecrease the amount of fluid 88 pumped by pump 44. This exemplarymovement profile may be defined manually by physician 30, orautomatically by processor 39 in response to receiving one or moresignals related to the medical procedure.

In other embodiments, controller 33 may control pump to stand withoutmoving at any suitable predefined distance from wall 66 and/or 77,typically located within interval 311.

In some embodiments, controller 33 is configured to choose betweenoperating pump 44 in an ablation state 300, typically during tissueablation, and non-ablation 333 state, typically between ablations. Insome cases, controller 33 receives an instruction signal from processor39 to switch between states 300 and 333.

In some embodiments, in ablation state 300, which corresponds to theaforementioned second operational mode, controller 33 is configured tocontrol piston 99 to move at a selected speed between walls 66 and 77.The selected speed may be constant during the ablation of all ablationsites in heart 26, or may vary between specific ablation sites in heart26 in response to different ablation conditions (e.g., time, temperatureand RF energy applied to tissue). Moreover, during ablation at aspecific ablation site, controller 33 may change the movement speed ofpiston 99, for example, in response to changes in the temperaturemeasured at the ablation site. In other words, controller 33 isconfigured to control piston 99 to move at a variable speed during thetissue ablation.

In some embodiments, controller 33 operates pump 44 at ablation state300 when piston is positioned within predefined interval 322, which isout of and not overlapping with intervals 311. The movement speeds ofshaft 105 during predefined distance interval 322 can be in accordancewith the movement speeds of shaft 105 described in relation to FIG. 3B.

In other embodiments, controller 33 may choose to switch from the firstoperational mode (i.e., at non-ablation state 333) to the secondoperational mode (i.e., at ablation state 300) when piston 99 is stillsituated within interval 311. Similarly, controller 33 may choose toswitch back from the second operational mode to the first operationalmode after piston 99 is already situated within interval 311 at theother end of cylinder 111.

In an embodiment, processor 39 may send a first instruction signal tocontroller 33 to switch to ablation state 300 when piston is withininterval 311, in close proximity to wall 66, and a second instructionsignal to switch back to non-ablation state 333 when piston is withininterval 311, in close proximity to wall 77. In this example embodimentshown in FIG. 5, the arrow representing ablation state 300 starts withininterval 311 situated in close proximity to wall 66, and terminateswithin interval 311 situated in close proximity to wall 77. In suchembodiments, controller 33 is configured to operate pump 44 in ablationstate 300 until piston 99 makes physical contact with wall 77.

In other embodiments, controller 33 is configured to choose between thefirst and second operational modes independently of processor 39. Forexample, in response to receiving, from PPSA 54, position signalsindicating that piston 99 is situated within interval 311, controller 33may switch from ablation state 300 of the second operational mode, tonon-ablation state 333 of the first operational mode.

Additionally or alternatively, controller 33 is configured to choosebetween the first and second operational modes using other sequences,for example, after irrigating an ablation site of heart 26 with apredefined volume of fluid 88, or based on any other suitable signal, orby using any suitable sequence programmed in controller 33.

This particular sequence of FIG. 5 is shown by way of example, in orderto illustrate certain problems, such as having sufficient fluid 88 forirrigating tissue during ablation using a pump. As described above,these problems are addressed by embodiments of the present inventionthat also demonstrate the application of these embodiments in enhancingthe performance of a pump operating in a cardiac ablation system.Embodiments of the present invention, however, are by no means limitedto these specific sorts of example pump and system, and the principlesdescribed herein may similarly be applied to other sorts of pumps andmedical ablation systems.

FIG. 6 is a flow chart 400 that schematically illustrates a method forpumping irrigation fluid 88 in a cardiac ablation procedure carried outby irrigation assembly 11, in accordance with another embodiment of thepresent invention. The method begins at a first piston movement step402, with controller 33 controlling the move of piston 99 at a selectedspeed in the direction shown by the arrow of ablation state 300. Notethat at step 402, controller 33 operates pump 44 in the secondoperational mode during the ablation of tissue in heart 26, and controlspiston 99 to move toward wall 77.

At a position signal receiving step 404, controller receives from PPSA54 signals indicative of the respective positions of piston 99 movedtoward wall 77, as described in FIG. 3B above. At a piston oscillatingstep 406, in response to receiving a position signal indicating thatpiston 99 is situated in close proximity to wall 77 within interval 311,controller 33 controls piston 99 to oscillate over interval 311 usingnon-ablation state 333, as described in FIG. 5 above.

At a control signal receiving step 408, controller 33 receives (e.g.,from processor 33) a control signal indicative of starting the tissueablation in heart 26. Note that the first irrigation depicted in step402 is carried out when distal end 22 is positioned at a first ablationsite, and the control signal of step 408 is received when distal end 22is typically positioned at a second, different, ablation site.

At a second piston movement step 410, in response to receiving thecontrol signal, controller 33 switches the operational mode of pump 44and controls piston 99 to move toward wall 66 for irrigating tissue withfluid 88 during the ablation of the second ablation site. In someembodiments, controller 33 controls piston 99 to move at the speedselected at step 402 above, but in the opposite direction, i.e., towardwall 66. In other embodiments, the ablation parameters at the secondablation site may differ from the ablation parameters of the firstablation site, and therefore, the selected speed of step 410 may differfrom the selected speed at step 402 above, so as to carry out suitableirrigation with fluid 88 during the ablation process at the secondablation site.

In some embodiments, after concluding step 401, the method loops back tostep 404 and continues until the last ablation site has been ablated byphysician 30.

In some embodiments, pump 44 described in FIGS. 1-6 above, and the term“pump” that appears in the claims section may comprise a dual-actionpump or any other suitable type of pump.

Although the embodiments described herein mainly address tissueirrigation in cardiac ablation procedures, the methods and systemsdescribed herein can also be used in other applications, such as inother cardiac applications, in any type of ablation procedure applied totissue of any other organ.

It will thus be appreciated that the embodiments described above arecited by way of example, and that the present invention is not limitedto what has been particularly shown and described hereinabove. Rather,the scope of the present invention includes both combinations andsub-combinations of the various features described hereinabove, as wellas variations and modifications thereof which would occur to personsskilled in the art upon reading the foregoing description and which arenot disclosed in the prior art. Documents incorporated by reference inthe present patent application are to be considered an integral part ofthe application except that to the extent any terms are defined in theseincorporated documents in a manner that conflicts with the definitionsmade explicitly or implicitly in the present specification, only thedefinitions in the present specification should be considered.

1. A pump, comprising: a cylinder having first and second ends andcomprising first and second inlet-outlet ports, wherein each of thefirst and second inlet-outlet ports is configured to alternately intakea fluid to the cylinder and output the fluid from the cylinder; apiston, which is configured to be moved within the cylinder between thefirst and second ends by alternately reversing a direction of movementof the piston, so as to pump the fluid through the first and secondinlet-outlet ports; and a controller, which is configured to control themovement of the piston within the cylinder in one or more of first andsecond operational modes so that: (a) in the first operational mode, thepiston oscillates over a predefined interval that does not exceed apredefined distance from the first end or from the second end; or (b) inthe second operational mode the piston moves at a selected speed betweenthe first end and the second end.
 2. The pump according to claim 1,wherein the controller is configured to receive a signal indicative of aposition of the piston within the cylinder, and to control the movementof the piston based on the signal.
 3. The pump according to claim 1,wherein at least one of the first and second inlet-outlet ports iscoupled to a fluid reservoir via a first pipe, and to a catheter via asecond pipe, so as to irrigate tissue with the fluid during a medicalprocedure.
 4. The pump according to claim 3, wherein the medicalprocedure comprises tissue ablation by the catheter, and wherein thecontroller is configured to control the movement of the piston in thesecond operational mode in response to receiving a control signalindicative of the tissue ablation.
 5. The pump according to claim 4,wherein the tissue ablation comprises positioning the catheter at firstand second ablation sites, and wherein, in the second operational mode,the controller is configured to control the piston to: (a) move at afirst selected speed when the catheter is positioned at the firstablation site, and (b) move at a second, different, selected speed whenthe catheter is positioned at the second ablation site.
 6. The pumpaccording to claim 1, wherein, in the second operational mode, thecontroller is configured to control the piston to move at a constantspeed.
 7. The pump according to claim 1, wherein, in the secondoperational mode, the controller is configured to control the piston tomove at a variable speed.
 8. A method for pumping a fluid in a pumpcomprising a cylinder having first and second ends and comprising firstand second inlet-outlet ports for alternately in-taking a fluid to thecylinder and outputting the fluid from the cylinder by each of the firstand second inlet-outlet ports;, the method comprising: moving a pistonwithin the cylinder between the first and second ends by alternatelyreversing a direction of movement of the piston, so as to pump the fluidthrough the first and second inlet-outlet ports; and controlling themovement of the piston within the cylinder in one or more of first andsecond operational modes that includes: in the first operational mode,controlling the piston to oscillate over a predefined interval that doesnot exceed a predefined distance from the first end or from the secondend; or in the second operational mode, controlling the piston to moveat a selected speed between the first end and the second end.
 9. Themethod according to claim 8, wherein controlling the movement of thepiston comprises receiving a signal indicative of a position of thepiston within the cylinder, and controlling the movement of the pistonbased on the signal.
 10. The method according to claim 8, and comprisingirrigating tissue with the fluid during a medical procedure by couplingat least one of the first and second inlet-outlet ports to a fluidreservoir via a first pipe, and to a catheter via a second pipe.
 11. Themethod according to claim 10, wherein the medical procedure comprisestissue ablation by the catheter, and wherein controlling the movement ofthe piston according to the second operational mode in response toreceiving a control signal indicative of the tissue ablation.
 12. Themethod according to claim 11, wherein the tissue ablation comprisespositioning the catheter at first and second ablation sites, andwherein, in the second operational mode, controlling the movement of thepiston comprises controlling the piston to: (a) move at a first selectedspeed when the catheter is positioned at the first ablation site, and(b) move at a second, different, selected speed when the catheter ispositioned at the second ablation site.
 13. The method according toclaim 8, wherein, in the second operational mode, controlling themovement of the piston comprises controlling the piston to move at aconstant speed.
 14. The method according to claim 8, wherein, in thesecond operational mode, controlling the movement of the pistoncomprises controlling the piston to move at a variable speed.
 15. Apump, comprising: a cylinder having first and second ends and comprisingfirst and second inlet-outlet ports, wherein each of the first andsecond inlet-outlet ports is configured to alternately intake a fluid tothe cylinder and output the fluid from the cylinder; a piston, which isconfigured to be moved within the cylinder between the first and secondends by alternately reversing a direction of movement of the piston, soas to pump the fluid through the first and second inlet-outlet ports;and a controller, which is configured to control the movement of thepiston within the cylinder, in one or more of first and secondoperational modes so that: (a) in the first operational mode, the pistonto remain stationary at a predefined distance larger than zero from thefirst end or from the second end; or (b) in the second operational mode,the piston moves at a selected speed between the first end and thesecond end.
 16. The pump according to claim 15, wherein the controlleris configured to receive a signal indicative of a position of the pistonwithin the cylinder, and to control the movement of the piston based onthe signal.
 17. The pump according to claim 15, wherein at least one ofthe first and second inlet-outlet ports is coupled to a fluid reservoirvia a first pipe, and to a catheter via a second pipe, so as to irrigatetissue with the fluid during a medical procedure.
 18. The pump accordingto claim 17, wherein the medical procedure comprises tissue ablation bythe catheter, and wherein the controller is configured to choose thesecond operational mode in response to receiving a control signalindicative of the tissue ablation.
 19. The pump according to claim 18,wherein the tissue ablation comprises positioning the catheter at firstand second ablation sites, and wherein, in the second operational mode,the controller is configured to control the piston to: (a) move at afirst selected speed when the catheter is positioned at the firstablation site, and (b) move at a second, different, selected speed whenthe catheter is positioned at the second ablation site.
 20. The pumpaccording to claim 15, wherein, in the second operational mode, thecontroller is configured to control the piston to move at a constantspeed.